How the automotive air duct resistant muffler works

The working principle of the resistive muffler is mainly based on the reflection and interference of sound waves. Through the mutation of the pipe cross section or the bypass resonant cavity and other structures, the impedance changes during the sound propagation process, resulting in the reflection and interference of sound energy. This kind of muffler plays a big role in the optimization of car air ducts. Its structure is similar to a filter in electricity. Each small chamber with a tube is equivalent to a mesh of the filter and has its own inherent frequency characteristics.
When sound waves enter a resistant muffler, their frequency content is screened out by a carefully designed system of ducts and chambers. Only sound waves that are close to the natural frequency of a specific chamber can pass through smoothly, while sound waves of other frequencies will reflect back and forth in the chamber and interfere with each other, thereby achieving the purpose of silencing. This acoustic filtering effect makes resistant mufflers good  at canceling mid- and low-frequency noise.
Significant advantages and wide application
Resistant mufflers have significant advantages over other types of mufflers. First of all, it does not use porous sound-absorbing materials, so it has good performance in terms of high temperature resistance, moisture resistance, and airflow impact resistance. It is especially suitable for noise control in harsh working conditions such as automobile engines. Secondly, the resistant muffler has less resistance to air flow and will not cause large pressure losses, which is beneficial to maintaining the smoothness of the engine air intake system. In addition, its simple structure and easy maintenance are also one of the reasons why it is popular.